Battery Basics

There are three key components to the electrical system:

1. BatteryWhen your car's engine is off, the battery provides the required power to the rest of the system, as well as during start-up (cranking). It also supplements the power from the charging system during periods of high demand.

2. Charging SystemThis is the heart of the electrical system. It consists of three main components: the belt-driven alternator, various electrical circuits, and a voltage regulator. The alternator supplies power to the electrical system and recharges the battery after your car has started. Just like it sounds, the voltage regulator controls the voltage, keeping it within the operating range of the electrical system.

3. Starting SystemThis system consumes more electrical power than any other in your vehicle. The starting system consists of three components which work together: the ignition switch, the starter relay (also known as the solenoid), and the starter motor. The ignition switch controls the starter solenoid, which activates the starter motor. The starter motor then turns the engine until your car starts.

For a close-up view of a car battery, alternator and starter, use the interactive diagram below.

Hover over highlighted parts for expanded view.

Battery

Alternator

Starter

Battery Life

A car's battery typically lasts 3 to 5 years. We recommend having your battery checked twice a year.

Car batteries can grow weaker and fail when you:

Leave the headlights, interior lights, flashers or radio on while the car isn't running.

Use the air conditioner while the engine is off.

Don’t start the car for a long period of time.

Have a problem with the alternator. (It charges the battery when the car is running.)

Live in an area with extremely hot or cold temperatures.

Jump Starting a Dead Battery

The most common way to at least temporarily fix a dead battery is to jump start it. For that reason, you should keep a set of jumper cables in your trunk, and make sure they're in good shape with no frayed or bare wires.

Here are the steps for jump starting a battery:

Make sure your key is turned to the off position and all electrical accessories are turned off (the radio, heat, turn signals, etc.).

Park the "rescue" car and the car with the dead battery either nose-to-nose or side-by-side facing the same direction. (Do not let the vehicles touch.)

Open the hood and inspect the dead battery for any signs of damage. Never try to jump start a car if its battery is cracked and leaking acid.

Identify the positive and negative terminals on each battery.

Connect one of the jumper cables’ positive clamps (red) to the positive (+) terminal on the "rescue" car's battery.

Connect the other positive jumper cable clamp (red) to the positive (+) terminal on the dead battery.

Connect the closest of the jumper cables’ negative clamps (black) to the negative (-) terminal on the "rescue" car's battery.

Connect the other negative jumper cable clamp (black) to an unpainted bolt or metal bracket within the engine compartment of the “dead” car as far away as possible from the battery.

Start the “rescue” car first and let it run for a few minutes. Then, try to start the car with the dead battery. Once that car has started, remove the cables in the reverse order in which they were attached.

Let the car run for a few minutes before driving, and then drive the vehicle for at least 20 minutes so the battery has time to fully charge.

If, after following this process, the dead car still doesn't start, check the cables to make sure they’re properly connected. Allow the “rescue” car keep running for a few more minutes, then try to start the “dead” car again. If it still won't start, there may be another problem with the engine.

A Simple Tip for Prolonging Battery Life

When your battery is new or after it’s been thoroughly cleaned, apply a protective spray to the terminals (also known as posts). The spray will reduce the amount of corrosion that builds up on the posts. That’s important because corrosion can prevent your alternator from fully charging the battery as you drive your vehicle. Re-spray the posts about every six months.